In general, a liquid crystal display (LCD) and a plasma display panel (PDP) have become well known as typical large-sized display apparatuses.
Unlike the PDP, which is self-emissive, the LCD needs a backlight unit since the LCD is not self-emissive.
Based on the position of a light source, the backlight unit may be classified as an edge type backlight unit or a direct type backlight unit. In the edge type backlight unit, a light source is located at the left and right sides and/or the upper and lower sides of an LCD panel, and light is uniformly dispersed over the entire surface of the LCD panel using a light guide plate. As a result, light uniformity is high, and it is possible to remarkably reduce the thickness of the LCD panel.
In the direct type backlight unit, which is generally applied to display apparatuses larger than 20 inches, a plurality of light sources is located under a panel. The direct type backlight unit exhibits higher light efficiency than the edge type backlight unit. For this reason, the direct type backlight unit is mainly used for large-sized display apparatuses in which high luminance is critical.
A cold cathode fluorescent lamp (CCFL) is used as a light source for a conventional edge type or direct type backlight unit. In the backlight unit using the CCFL, however, electric power is constantly supplied to the CCFL, with the result that power consumption is too high. In addition, the CCFL exhibits a color gamut equivalent to about 70% that of a cathode ray tube (CRT). Furthermore, the CCFL causes environmental pollution due to mercury contained in the CCFL.
In recent years, research has been actively conducted into a backlight unit using light emitting diodes (LEDs) as a substitute that is capable of solving the above problems.
In a case in which LEDs are used for the backlight unit, it is necessary to reduce the cost of manufacturing the backlight unit, to reduce power consumption of the backlight unit, and to configure the backlight unit such that the backlight unit is slim.